Engine inlet air cooling system and method

ABSTRACT

A method of cooling inlet air to an engine includes pressurizing the inlet air during a first compression stage, and further pressurizing the inlet air during a second compression stage. Heat is transferred from the inlet air to a primary coolant liquid between the first compression stage and the second compression stage, and heat is transferred selectively, variably, or selectively and variably from the primary coolant liquid to a fuel of the engine.

TECHNICAL FIELD

The present disclosure relates generally to engine inlet air cooling systems. Specifically, an embodiment of the present invention relates to an inlet air cooling system with a first compressor, a second compressor, and a cooling circuit.

BACKGROUND

Compressing engine inlet air in two or more compression stages may benefit the efficiency of the combustion process of an internal combustion engine by driving more air into the combustion cylinder. Denser inlet air may also assist in meeting some governmental engine emission regulations. Compared to inlet air passing through just one compression stage, inlet air passing through two or more compression stages, may have a significantly higher temperature. Compressing higher temperature air requires additional work. Driving a turbine in the exhaust stream to drive a compression device in a second or subsequent compression stage, causes additional parasitic exhaust gas pumping, resulting in decreased engine efficiency. Cooling the inlet air between compression stages may allow the second or subsequent compressor devices to operate more efficiently. After the compression stage, inlet air is often passed through one or more air cooling devices, to assist in controlling the temperature of air entering an engine combustion chamber, which may allow increased fuel efficiency while meeting emission regulations. A more robust, and sometimes more expensive, air cooler may be needed when using two or more compression stages. In addition, more energy may be expended cooling the inlet air.

Some engine fuels, such as for example, liquid natural gas (LNG), hydrogen (H₂), ammonia (NH₃), and mixtures of H₂ and oxygen (O₂) are stored in cryogenic storage tanks or other cold storage, and must be heated prior to being combusted in an engine. The use of LNG has increased in some applications and geographic regions as the infrastructure to support use and lower fuel costs make is a desirable fuel. LNG, and other fuels, may be passed through a heat exchanger to both cool the inlet air and heat the fuel. However, if the inlet air has a high enough level of humidity, high levels of cooling may create ice crystals. If passed through some compressors, the ice crystals may cause damage.

U.S. Pat. No. 8,220,268 to Callas discloses an engine having a first compressor configured to pressurize inlet air, and a second compressor configured to further pressurize the inlet air. The engine may also have a cooling circuit fluidly located to cool the inlet air after the inlet air is pressurized by the first compressor and before the inlet air is further pressurized by the second compressor. The cooling circuit may have a first heat exchanger configured to transfer heat from the inlet air to a fuel of the engine, and a second heat exchanger configured to transfer heat from exhaust of the engine to the fuel of the engine.

SUMMARY OF THE INVENTION

In one aspect, a method of cooling inlet air to an engine includes pressurizing the inlet air during a first compression stage, and further pressurizing the inlet air during a second compression stage. Heat is transferred from the inlet air to a primary coolant liquid between the first compression stage and the second compression stage, and heat is transferred selectively, variably, or selectively and variably from the primary coolant liquid to a fuel of the engine.

In another aspect, an engine inlet air cooling system includes a first compressor configured to pressurize inlet air, a second compressor configured to further pressurize the inlet air, and a cooling circuit. The cooling circuit includes a coolant heat exchanger, an inlet air heat exchanger, and a fuel cooled heat exchanger. The coolant heat exchanger is configured to transfer heat from a primary coolant liquid. The inlet air heat exchanger is configured to transfer heat from the inlet air to the primary coolant liquid after the inlet air exits the first compressor and before the inlet air enters the second compressor. The fuel cooled heat exchanger is configured to selectively transfer heat from the primary coolant liquid to a fuel of the engine.

In another aspect, an engine inlet air cooling system includes an inlet air heat exchanger, a coolant heat exchanger, a fuel cooled heat exchanger, an inlet air circuit, a fuel circuit, and a primary coolant circuit. The inlet air heat exchanger includes an inlet air passage and a first primary coolant passage in thermal communication. The coolant heat exchanger includes a second primary coolant passage. The fuel cooled heat exchanger includes a fuel passage and a third primary coolant passage in thermal communication. The inlet air circuit includes a first compressor configured to pressurize inlet air, the inlet air passage, and a second compressor configured to further pressurize the inlet air, wherein the inlet air passage fluidly connects the first compressor and the second compressor. The fuel circuit includes the fuel passage. The primary coolant circuit includes the first primary coolant passage, the second primary coolant passage, the third primary coolant passage, a fuel cooled heat exchanger bypass, and a control valve assembly. The second primary coolant passage fluidly connects to the first primary coolant passage. The third primary coolant passage fluidly connects to the first primary coolant passage. The fuel cooled heat exchanger bypass fluidly connects to the first primary coolant passage. The control valve assembly selectively fluidly connects the second primary coolant passage to the bypass, and selectively fluidly connects the second primary coolant passage to the third primary coolant passage.

In another aspect, an engine system includes an engine, a fuel source, a first compressor configured to pressurize inlet air, a second compressor configured to further pressurize the inlet air, and a cooling circuit. The engine includes an intake manifold, and a fueling device the second compressor fluidly connects to the intake manifold. The cooling circuit includes a coolant heat exchanger, an inlet air heat exchanger, and a fuel cooled heat exchanger. The coolant heat exchanger is configured to transfer heat from a primary coolant liquid. The inlet air heat exchanger is configured to transfer heat from the inlet air to the primary coolant liquid after the inlet air exits the first compressor and before the inlet air enters the second compressor. The fuel cooled heat exchanger is configured to selectively transfer heat from the coolant liquid to a fuel of the engine, and fluidly connects the fueling device and the fuel source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts an exemplary embodiment of an engine inlet air cooling system.

FIG. 2 schematically depicts another exemplary embodiment of an engine inlet air cooling system.

FIG. 3 depicts a flow chart of an exemplary method of cooling inlet air to an engine.

DETAILED DESCRIPTION

Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding or similar reference numbers will be used, when possible, to refer to the same or corresponding parts.

Referring now to FIG. 1, an exemplary embodiment of an air inlet system 100 is illustrated. The air inlet system 100 includes a first compressor 102 configured to pressurize inlet air, and a second compressor 104 configured to further pressurize the inlet air. The air inlet system 100 provides compressed air to an engine 140. In one embodiment, the engine 140 may include an internal combustion engine with an intake manifold 142. In the internal combustion engine embodiment, the first and second compressors 102, 104 may be compressors of a twin compressor turbocharger or supercharger. Alternatively, the first and second compressors 102, 104 may be compressors in a series arrangement of turbochargers or superchargers. In other embodiments the engine 140 may include a turbine engine and the compressors 102, 104 may include compressor sections of the turbine engine.

The inlet air system 100 further includes a cooling circuit 106 including an first inlet air heat exchanger 108 configured to transfer heat from the inlet air to a primary coolant liquid after the inlet air exits the first compressor 102 and before the inlet air enters the second compressor 104. The first inlet air heat exchanger 108 may include a first inlet air passage 110 in thermal communication with a first primary coolant passage 112. As the inlet air flows through the first inlet air passage 110, thermal energy 114 may be transferred to primary coolant liquid flowing through the primary coolant passage 112. The first inlet air heat exchanger 108 may include a double pipe heat exchanger, a shell and tube heat exchanger, or any other heat exchanger known in the art. The primary coolant may include water, glycol, another refrigerant, or any other coolant as known in the art.

The cooling circuit 106 includes a coolant heat exchanger 116 configured to transfer heat from the primary coolant liquid. In the illustrated embodiment, the coolant heat exchanger 116 includes a radiator type heat exchanger including a second primary coolant passage 118, a fan shroud 120, and a fan 122. The fan 122 may direct a secondary coolant 124, illustrated as air, through the coolant heat exchanger 116. Heat from the primary coolant liquid in the second primary coolant passage 118 may be transferred to the air as it is directed through the coolant heat exchanger 116. In other embodiments the coolant heat exchanger 116 may include other heat exchangers known in the art.

The cooling circuit 106 includes a fuel cooled heat exchanger 126 configured to selectively transfer heat from the primary coolant liquid to a fuel of the engine 140. The fuel cooled heat exchanger 126 may include a first fuel passage 128 in thermal communication with a third primary coolant passage 130. As primary coolant liquid selectively flows through the third primary coolant passage 130, thermal energy 132 may be transferred to fuel flowing through the first fuel passage 128. The fuel heat exchanger 126 may include a double pipe heat exchanger, a shell and tube heat exchanger, or any other heat exchanger known in the art. The fuel may include a cryogenically stored fuel such as LNG, H₂, NH₃, or mixtures of H₂ and O₂, or any other engine fuel as known in the art.

The inlet air system 100 includes an inlet air circuit 134 fluidly connecting inlet air from the environment (not shown) surrounding the engine 140, or another inlet air source (not shown) to the engine 140. The inlet air circuit 134 includes the first compressor 102 and the second compressor 104. The inlet air circuit 134 may include the first inlet air passage 110 fluidly connecting the first compressor 102 and the second compressor 104. In the embodiment illustrated, elements of the inlet air circuit 134 are fluidly connected by air conduits 136 illustrated by solid lines with no cross hatches.

The inlet air circuit 134 may include a second inlet air heat exchanger 138 fluidly connecting the second compressor 104 to the engine 140. The second inlet air heat exchanger 138 may be configured to transfer heat from the inlet air to another medium after the inlet air exits the second compressor 102 and before the inlet air enters the engine 140. The second inlet air heat exchanger 138 may include a second inlet air passage 135 in thermal communication with a second fuel passage 143. A valve 137 may selectively direct fuel through the second fuel passage 143. As the inlet air flows through the second inlet air passage 135, thermal energy 139 may be transferred to fuel flowing through the second fuel passage 143. The second inlet air heat exchanger 138 may include a double pipe heat exchanger, a shell and tube heat exchanger, or any other heat exchanger known in the art. Although illustrated as a fuel cooled heat exchanger, in other embodiments the other mediums may be used as coolants as are known in the art. Some embodiments of the inlet air circuit 134 may not include the second inlet air heat exchanger 138.

Inlet air may flow into the inlet air circuit 134, flow through and be pressurized by the first compressor 102, flow through the first inlet air passage 110 and transfer heat to the primary coolant liquid, flow through and be further pressurized by the second compressor 104, flow through the second inlet air passage 135 and transfer heat to the fuel, and flow into the intake manifold 142 of the engine 140, as illustrated by the outlined arrows.

In the illustrated embodiment, the system 100 includes a fuel circuit 144 fluidly connecting a fuel source 146 with a fueling device 148. The fuel circuit 144 may provide fuel for the engine 140, direct fuel through the first fuel passage 128, and selectively direct fuel through the second fuel passage 143. The fueling device 148 may include a fuel injector 150. Fuel conduits 152, illustrated by solid lines with double cross hatches, may fluidly connect elements of the fuel circuit 144. Fuel may flow from the fuel source 146, flow through the first fuel passage 128 and absorb thermal energy from the primary coolant, selectively flow through the second fuel passage 143 and absorb thermal energy from the inlet air, flow to the fuel injector 150, and be injected into the engine 140 during the combustion process. Valve 137 may be actuated to control the flow of fuel through the second fuel passage 143. A check valve 141 may aid in ensuring the desired direction of fuel flow through the second fuel passage 143. Fuel flow is illustrated by the patterned arrows.

In the illustrated embodiment, the inlet air system 100 includes a primary coolant circuit 154 including the first primary coolant passage 112, the second primary coolant passage 118, a primary coolant bypass 156, a primary coolant circuit branch 157, and a control valve assembly 158 for selectively, variably, or selectively and variably directing primary coolant liquid through the bypass 156 and/or the branch 157. The control valve assembly 158 may include a variable orifice valve 160 for directing and varying the flow of primary coolant liquid into the bypass 156, and a variable orifice valve 162 for directing and varying the flow of primary coolant liquid into the branch 157. The primary coolant circuit 154 may also include a pump 164 for pressurizing primary coolant liquid to flow through the primary coolant circuit 154. The pump 164 is illustrated as a fixed displacement, unidirectional pump and may be driven by a mechanical link to engine 140. In other embodiments, the pump 164 may include a variable displacement pump, and may be driven by other power sources such as an electric motor. Although illustrated as a single unit, pump 164 may also include multiple pumps placed at one or multiple locations in the primary coolant circuit 154.

The primary coolant circuit 154 may include a mixing valve assembly 166 for mixing primary coolant liquid from the bypass 156 and the branch 157. Primary coolant conduits 168, illustrated by the solid lines with a single cross hatch, may fluidly connect elements of the primary coolant circuit 154.

Primary coolant liquid may flow from the first primary coolant passage 110, flow through the second primary passage 118 and transfer thermal energy to the secondary coolant liquid, flow through and be pressurized by the pump 164, flow through the control valve assembly 158, and be selectively, variably, or selectively and variably directed into the bypass 156 and/or the branch 157. Some or all of the primary coolant liquid flow from the pump 164 may be directed through the variable orifice valve 160 into the bypass 156 and flow to the mixing valve 166. Some or all of the primary coolant liquid flow from the pump 164 may also, or alternatively, be directed through the variable orifice valve 162 into the branch 157, flow through the third primary coolant passage 130 and transfer thermal energy to the fuel, and flow to the mixing valve 166. Primary coolant liquid from the bypass 156 and the branch 157 may flow through and be mixed by the mixing valve 166, and then flow through the first primary coolant passage 112 and absorb thermal energy from the inlet air. The flow of primary coolant liquid is illustrated by the solid arrows.

To selectively, variably, or selectively and variably control the transfer of heat from the primary coolant liquid to the fuel, the system 100 may include an electronic or computerized control unit, module, or controller 202. The controller 202 may receive signals generated by sensors and/or calculated as functions of various system and/or engine parameters, and coordinate and control the flow of the primary coolant through the bypass 156, and/or the branch 157 as a function of the signals and/or parameters. The controller 202 may also coordinate and control other components or functions associated with the engine 140 and/or the inlet air system 100, such as, for example, fuel injections by the fuel injector 150.

The controller 202 can include a microprocessor, an application specific integrated circuit (ASIC), or other appropriate circuitry and can have memory or other data storage capabilities. The controller 202 can include functions, steps, routines, data tables, data maps, charts, and the like, saved in, and executable from, read only memory, or another electronically accessible storage medium, to control the engine 140 and air inlet system 100. Although the controller 202 is illustrated as a single, discrete unit, in other embodiments, the controller 202 and its functions may be distributed among a plurality of distinct and separate components. The single unit or multiple component controller 202 may be located on-board the engine 140 or a machine associated with the air inlet system 100, and/or in a remote location. To receive operating parameters and send control commands or instructions, the controller 202 can be operatively associated with and can communicate with various sensors and controls on the engine 140 and air inlet system 100. Communication between the controller 202 and the sensors can be established by sending and receiving digital or analog signals across electronic communication lines or communication busses. In some embodiments the communication between the controller 202 and the sensors may be by radio, satellite, and/or telecommunication channels. These communication connections are illustrated with dashed lines.

To measure the flow rate, pressure and/or temperature of the inlet air at various locations in the inlet air circuit 134, the controller 202 can be communicatively connected with one or more inlet air sensors 203. The inlet air sensors 203 may also determine or sense the barometric pressure, humidity, or other environmental conditions in which the engine 140 and inlet air system 100 is operating. In the illustrated embodiment, exemplary air sensors 203 include a humidity sensor 204, a first inlet air temperature sensor 206, and a second inlet air temperature sensor 208. The humidity sensor 204 is disposed at or near the location that the inlet air enters the inlet air circuit 134, and is configured to generate a signal indicative of the humidity of the inlet air. The first temperature sensor 204 is disposed between the first compressor 102 and the first inlet air passage 110 and is configured to generate a signal indicative of the temperature of the inlet air flowing out of the first compressor 102. The second temperature sensor 206 is disposed between the second compressor 104 and the second inlet air heat exchanger 138, and is configured to generate a signal indicative of the temperature of the inlet air flowing out of the second compressor 104. In other embodiments other inlet air sensors 203 may be disposed at other locations in the inlet air circuit 134 to sense characteristics of the inlet air at those locations.

To monitor the temperature of the primary coolant liquid at various locations in the coolant circuit 154, the controller 202 can be communicatively connected with one or more coolant temperature sensors 210. Although only one coolant temperature sensor 210, located between the mixing valve 166 and the first primary coolant passage 112, is illustrated, additional coolant temperature sensors 210 may be located at other locations in the coolant circuit 154. The controller 154 may receive temperature signals from the one or more coolant temperature sensors 210 and may calculate temperatures at other locations in the coolant circuit 154.

The controller 202 can be communicatively connected to and control the actuation of the control valve assembly 158 to control the flow of primary coolant liquid through the third primary coolant passage 130. As illustrated, the controller 202 is communicatively connected to a variable orifice valve 160 to control the flow of primary coolant through the bypass 156, and to a variable orifice valve 162 to control the flow of primary coolant liquid through the branch 157. Those skilled in the art will realize that other configurations of the control valve assembly 158 are possible to control the flow of primary coolant liquid through the third primary coolant passage 130, and these configurations are contemplated embodiments. Controller 202 can be communicatively connected to and control the actuation of valve 137 to selectively, variably, or selectively and variable control the flow of fuel through second fuel passage 143.

Referring now to FIG. 2, another exemplary embodiment of air inlet system 100 is illustrated. In this embodiment a third compression stage is added; inlet air flows through a third inlet air heat exchanger 180 between the second and third compression stages; and the fuel cooled second inlet heat exchanger 138, fuel passage 143 and associated valves 137, 141 are not included. An alternative embodiment of the fuel heat exchanger 126 may transfer thermal energy from primary coolant to the fuel through a conductive liquid. The valve assembly 158 selectively, variably, or selectively and variably directs primary coolant through a fourth primary coolant passage 174 (in addition to the third primary coolant passage 130) included in the fuel heat exchanger 126. Primary coolant flows to both the first inlet air heat exchanger 108 and the third inlet air heat exchanger 180, in parallel, after exiting the fuel heat exchanger 126 and/or bypass 156 and a second bypass 188. Elements of the embodiment of system 100 in FIG. 2 not described below are similar to those shown and described in relation to FIG. 1.

The inlet air circuit 134 in the illustrated embodiment includes a third compressor 170, and a third inlet air heat exchanger 180. The third compressor 170 is configured to further pressurize inlet air flowing from the second compressor 104 and provide the compressed air to the engine. Similar to the other compressors 102, 104, the third compressor 170 may be a compressor in a turbocharger or other supercharger, or a compressor section of a turbine engine.

The third inlet air heat exchanger 180 is configured to transfer heat from the inlet air to the primary coolant liquid after the inlet air exits the second compressor 104 and before the inlet air enters the third compressor 170. The third inlet air heat exchanger 170 may include a third inlet air passage 182 in thermal communication with a fifth primary coolant passage 184. As the inlet air flows through the third inlet air passage 182, thermal energy 186 may be transferred from the inlet air to primary coolant liquid flowing through the fifth primary coolant passage 184. The third inlet air heat exchanger 180 may include a double pipe heat exchanger, a shell and tube heat exchanger, or any other heat exchanger known in the art.

Inlet air may flow into the inlet air circuit 134, flow through and be pressurized by the first compressor 102, flow through the first inlet air passage 110 and transfer heat to the primary coolant liquid, flow through and be further pressurized by the second compressor 104, flow through the third inlet air passage 182 and transfer heat to the primary coolant liquid, flow through and be further pressurized by the third compressor 170, and flow into the intake manifold 142 of the engine 140, as illustrated by the outlined arrows. Although not illustrated in FIG. 2, a second inlet air heat exchanger 138, as shown and described in relation to FIG. 1, may cool the inlet air between the third compressor 170 and the engine 140.

In the alternative embodiment of the fuel cooled heat exchanger 126, the first fuel passage 128 may include several coolant passages; and the third primary coolant passage 130 may include multiple cooling passages 172, through which the primary coolant variably, selectively, or variably and selectively flows. The fuel cooled heat exchanger 126 may additionally include the fourth primary coolant passage 174 including multiple coolant passages 172 through which the primary coolant variably, selectively, or variably and selectively flows. The first fuel passage 128, third primary coolant passage 130, and fourth primary coolant passage 174 may be surrounded by a thermally conductive liquid 178 contained in a tank through which the passages 128, 130, 174 are routed through. As primary coolant liquid selectively flows through the third primary coolant passage 130, and/or the fourth primary coolant passage 174, thermal energy may be transferred to the conductive liquid 178, and from the conductive liquid 178 to the fuel flowing through the first fuel passage 128.

In the illustrated embodiment, the primary coolant circuit 154 additionally includes the fifth primary coolant passage 184 of the third inlet air heat exchanger 180; and the fourth primary coolant passage 174 and a second coolant bypass 188 for selectively, variably, or selectively and variably directing primary coolant to the fifth primary coolant passage 184. The control valve assembly 158 alternatively includes two selective and variable valves 176. The pump 164 may be selectively, variably, or selectively and variably connected with the third primary coolant passage 130 and/or the bypass 156 through one of the valves 176. The valve 176 may direct fluid from the pump to any of, or all of the multiple passages 172 and/or the bypass 156. After primary coolant passes through the third primary coolant passage 130 and/or the bypass 156, the primary coolant flows into the mixing valve 166 and then to the first primary coolant passage 112. The pump 164 may also be selectively, variably, or selectively and variably connected with the fourth primary coolant passage 174 and/or the second bypass 188 through the other valve 176. The valve 176 may direct fluid from the pump to any of, or all of the multiple passages 172 and/or the bypass 188. After primary coolant passes through the fourth primary coolant passage 174 and/or the bypass 188, the primary coolant flows into the mixing valve 166 and then to the fifth primary coolant passage 184.

Primary coolant liquid may flow from the first primary coolant passage 112, flow through the second primary coolant passage 118 and transfer thermal energy to the secondary coolant liquid, flow through and be pressurized by the pump 164, flow through the control valve assembly 158, and be selectively, variably, or selectively and variably directed into the third primary coolant passage 130, the fourth primary coolant passage 174, the bypass 156, and/or the second bypass 188. Primary coolant liquid flowing through the third primary coolant passage 130 and the fourth primary coolant passage 174 may transfer thermal energy to the conductive liquid 178 which may transfer thermal energy to the fuel. Primary coolant liquid from the third coolant passage 130 and the bypass 156 may flow through and be mixed by the mixing valve 166, and then flow through the first primary coolant passage 112 and absorb thermal energy from the inlet air. Primary coolant liquid from the fourth coolant passage 174 and the second bypass 188 may flow through and be mixed by the mixing valve 166, flow through the fifth primary coolant passage 184 and absorb thermal energy from the inlet air, and then flow back through the second primary coolant passage 118.

The controller 202 may receive signals generated by sensors and/or calculated as functions of various system and/or engine parameters, and coordinate and control the flow of the primary coolant through the third primary coolant passage 130, the fourth primary coolant passage 174, the bypass 156, and/or the second bypass 188 as a function of the signals and/or parameters.

In the embodiment of FIG. 2, the inlet air sensors 203 additionally include a third inlet air temperature sensor 212, and a fourth inlet air temperature sensor 214. The third temperature sensor 212 is disposed between the third inlet air passage 182 and the third compressor 170, and is configured to generate a signal indicative of the temperature of the inlet air flowing out of the third inlet air heat exchanger 180. The fourth temperature sensor 214 is disposed between the third compressor 170 and the intake manifold 142, and is configured to generate a signal indicative of the temperature of the inlet air flowing out of the third compressor 170.

The coolant temperature sensors 210 of the embodiment illustrated in FIG. 2 include one coolant temperature sensor 210 located between the mixing valve 166 and the first primary coolant passage 112, and another coolant temperature sensor 210 located between the mixing valve 166 and the fifth primary coolant passage 184. The coolant temperature sensors 210 are communicatively connected to the controller 202.

In the illustrated embodiment, the controller 202 is communicatively connected to and controls the actuation of the control valve assembly 158 to selectively, variably, or selectively and variably control the flow of primary coolant liquid through the third primary coolant passage 130, the fourth primary coolant passage 174, the bypass 156, and the second bypass 188.

INDUSTRIAL APPLICABILITY

Cooling the inlet air to an engine 140 between compression stages may assist in raising the efficiency of the second compressor 104 and/or third compressor 170 and in reducing the level of cooling needed after the final compression stage, before the inlet air enters the intake manifold 142. Transferring heat to a fuel stored cryogenically, may not only cool the inlet air, but may provide necessary heat to the fuel as well, making the system 100 more efficient. In some circumstances, such as high humidity, it may be necessary to control cooling before or between compression stages to prevent ice crystals formation which might damage a compressor 104, 170 or other undesirable conditions.

Referring now to FIG. 3, a flow chart of an exemplary method 300 of cooling inlet air to an engine is illustrated. The method 300 includes pressurizing the inlet air during a first compression stage, further pressurizing the inlet air during a second compression stage, transferring heat from the inlet air to a primary coolant liquid between the first compression stage and the second compression stage, and selectively, variably, or selectively and variably transferring heat from the primary coolant liquid to a fuel of the engine.

The method 300 starts at step 302 and proceeds to step 304. In step 304 inlet air is pressurized during a first compression stage. In the embodiment of the air inlet cooling system 100 illustrated in FIG. 1, inlet air enters the inlet air circuit 134 and is pressurized in the first compressor 102. As the inlet air is compressed, the inlet air temperature rises. The method 300 proceeds to step 306. In step 306 heat is transferred from the inlet air to a primary coolant liquid between the first compression stage and the second compression stage. In the embodiment of the air inlet cooling system 100 illustrated in FIG. 1, the inlet air flows through the first inlet air passage 110 of the first inlet air heat exchanger 108 between the first compression stage and the second compression stage. The first inlet air passage 110 is in thermal communication with the first primary coolant passage 112 of the first inlet air heat exchanger 108, and heat is transferred from the inlet air flowing through the first inlet air passage 110 to the primary coolant liquid flowing through the first primary coolant passage 112. The method 300 proceeds to step 308.

In step 308, the inlet air is further pressurized during a second compression stage. In the embodiment of the air inlet cooling system 100 illustrated in FIG. 1, the inlet air flows from the first compressor 102, through the first inlet air passage 110 and enters the second compressor 104, where the inlet air is further pressurized. The method 300 proceeds to step 310.

In step 310, heat is transferred from the primary coolant liquid to a secondary coolant liquid. After absorbing thermal energy while flowing through the first primary coolant passage 112, the primary coolant liquid in the embodiment of system 100 of FIG. 1, flows into and through the second primary coolant passage 118 of the coolant heat exchanger 116. The secondary coolant liquid 124 is directed through the coolant heat exchanger 116 by the fan 122 and fan shroud 120. Heat is transferred from the primary coolant liquid flowing through the second primary cooling passage 118 to the secondary coolant liquid 124. The method 300 proceeds to step 312.

In step 312, heat is selectively transferred from the primary coolant liquid to a fuel of the engine 140 with a fuel heat exchanger 126. In the embodiment of system 100 illustrated in FIG. 1, some or all of the primary coolant liquid may be directed into the circuit branch 157, and thus into the third primary coolant passage 130. The primary coolant liquid flows from the second primary coolant passage 118, and then flows through and is pressurized by the pump 164, and flows into the control valve assembly 158. The control valve assembly 158 may selectively direct some or all of the primary coolant liquid into the third primary coolant passage 130 of the fuel cooled heat exchanger 126. Thermal energy is transferred from primary coolant liquid flowing through the third primary coolant passage 130 to fuel flowing through the first fuel passage 128 of the fuel cooled heat exchanger 126.

In the embodiment of system 100 illustrated in FIG. 2, the control valve assembly 158 may direct primary coolant liquid through one, some, all, or none of the multiple coolant passages 172 of the third primary coolant passage 130 and the fourth primary coolant passage 174, and/or the bypass 156 and second bypass 188. The controller 202 may control the valves 176 to select which of the multiple coolant passages 172 and bypasses 156, 188 to direct primary coolant through as a function of desired thermal energy transfer 114, 186 in the inlet air heat exchangers 108, 180. Thermal energy is transferred from primary coolant liquid flowing through the third primary coolant passage 130 and the fourth primary coolant passage to fuel flowing through the first fuel passage 128 of the fuel cooled heat exchanger 126.

It may be necessary to heat fuel stored cryogenically, or by other cold storage methods, before the fuel may be used in the combustion process of the engine 140. In the embodiments of system 100, illustrated in FIGS. 1 and 2, fuel may be stored cryogenically in fuel source 146. Fuel source 146 may, for example, include a cryogenic fuel tank for storing LNG. LNG may flow from the fuel source 146 through first fuel passage 128. Thermal energy may be transferred to the LNG flowing through first fuel passage 128 from primary coolant liquid flowing through the third primary coolant passage 130. The heated LNG may flow through other fuel conditioning and heating devices (not shown) to fueling device 150, and be injected into a combustion chamber of the engine 140. By transferring thermal energy from the primary coolant liquid to the LNG in the fuel cooled heat exchanger, energy which might have been needed to heat the LNG, or cool the primary coolant liquid may be saved. The method proceeds to step 314.

In steps 314, 316, 318, and 320, system 100 parameters are determined. In system 100, as illustrated in FIG. 1, these parameters may be used to control the flow of primary coolant liquid directed through the branch 157, and thus the fuel cooled heat exchanger 126, and/or to control the flow of primary coolant liquid directed through the bypass 156. In system 100, as illustrated in FIG. 2, these parameters may be used to control the flow of primary coolant liquid directed through one, some, all or none of the multiple coolant passages 172, and thus the fuel cooled heat exchanger 126, and/or the bypasses 156, 188. In both illustrated embodiments, in step 314, the inlet air temperature sensor 306 generates a signal indicative of the temperature of the inlet air when it exits the first compressor 102. In both illustrated embodiments, in step 316, the inlet air temperature sensor 208 generates a signal indicative of the temperature of the inlet air when it exits the second compressor 104. In both illustrated embodiments, in step 318, the humidity sensor 204 generates a signal indicative of the humidity of the inlet air as it enters the inlet air circuit 134. In both illustrated embodiments, in step 320, the coolant temperature sensor 210 generates a signal indicative of the temperature of the primary coolant liquid as it flows into the first primary coolant passage 112. In the embodiment illustrated in FIG. 2, a second coolant temperature sensor 210 generates a signal indicative of the temperature of the primary coolant liquid as it flows into the fifth primary coolant passage 184. The controller 202 may receive the sensor 204, 206, 208, 210 signals and generate command signals to the control valve assembly 158 as a function of the sensor 204, 206, 208, 210 signals and other system 100 or engine 140 parameters. In the embodiment illustrated in FIG. 2, other parameters may include a signal generated by inlet air temperature sensor 212 indicative of the temperature of the inlet air as it enters the third compressor 170; and a signal generated by inlet air temperature sensor 214 indicative of the temperature of the inlet air as it exits the third compressor 170. The method 300 proceeds to step 322.

In step 322, as illustrated in FIG. 1, the controller 202 may control the actuation of the control valve assembly 158 to direct some or all of the primary coolant liquid through the bypass 156 as a function of the inlet air temperature and humidity, and the primary coolant liquid temperature. In the embodiment illustrated in FIG. 2, the controller 202 may control the actuation of the control valve assembly 158 to direct primary coolant liquid through one, some, all, or none of the multiple coolant passages 172 and/or the bypasses 156, 188 as a function of the inlet air temperature and humidity, and the primary coolant liquid temperature. The controller 202 may include logic in a memory which may be executed on a processor to ensure that the temperature of the inlet air exiting the second compressor 104 (and/or third compressor 170 in relation to FIG. 2) does not exceed a maximum air temperature value. That maximum air temperature value may be set to ensure that the second inlet air heat exchanger 138 and/or other air inlet circuit elements are not damaged. The controller 202 may also include logic to ensure that inlet air exiting the first inlet air heat exchanger 108 (and third inlet air exchanger 180 in relation to FIG. 2) does not include ice crystals which may damage the second compressor 104 (and/or third compressor 170 in relation to FIG. 2). The logic may be in the form of tables, equations, or other functions as is known in the art. Examples of logic may include directing all or most of the flow of primary coolant liquid through the branch 157 (or the third coolant passage 130 and fourth coolant passage 174 in relation to FIG. 2), and thus the fuel cooled heat exchanger 126, when the inlet air humidity is below a set humidity value such that ice crystals may not form. The logic may include dividing the flow of the primary coolant liquid when inlet air humidity is above the set humidity value, between the branch 157 (or the third coolant passage 130 and fourth coolant passage 174 in relation to FIG. 2) and the bypass 156 (and/or second bypass 188 in relation to FIG. 2), such that the temperature of the flow of inlet air into the second compressor 104 (and/or third compressor 170 in relation to FIG. 2) is high enough that ice crystals may not form, and the temperature of the flow of inlet air exiting of the second compressor 104 (and/or third compressor 170 in relation to FIG. 2) is low enough that inlet air circuit 134 elements are not damaged. The temperature of inlet air entering the second compressor 104 may be calculated as a function of the inlet air temperature exiting the first compressor 102, the primary coolant temperature entering the first inlet air heat exchanger 108, and the geometry of the system 100, as would be known in the art. Similar calculations may be used to determine the temperature of inlet air entering the third compressor 170 in FIG. 2. In another embodiment, a sensor (not shown) could measure the temperature directly. The amount of primary coolant liquid flow required in the bypass 156 (and/or second bypass 188 in relation to FIG. 2) and/or in the branch 157 (or multiple coolant passages 172 in relation to FIG. 2) to achieve the desired inlet air temperature may be calculated as a function of system 100 or engine parameters and the geometry of the system through algorithms, look-up tables, maps, or other methods as are known in the art. The controller 202 may actuate the control valve assembly 158 to achieve the desired flows as is known in the art. The method 300 proceeds to step 324.

In step 324, primary coolant liquid from the bypass circuit 156 (and secondary bypass circuit 188 for FIG. 2) and primary coolant exiting the fuel heat exchanger 126 are mixed. In the embodiment illustrated in FIG. 1, primary coolant liquid from the branch 157 and the bypass 156 are directed into a mixing valve 166, and then directed into the first primary coolant passage 112. In the embodiment illustrated in FIG. 2, primary coolant from the third primary coolant passage 130 and the bypass circuit 156 are directed into a mixing valve 166, and then directed into the first primary coolant passage 112. In addition, primary coolant from the fourth primary coolant passage 174 and the second bypass circuit 188 are directed into a mixing valve 166, and then directed into the fifth primary coolant passage 184.The method proceeds to step 326 and ends.

It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 

What is claimed is:
 1. A method of cooling inlet air to an engine, comprising pressurizing the inlet air during a first compression stage; further pressurizing the inlet air during a second compression stage; transferring heat from the inlet air to a primary coolant liquid between the first compression stage and the second compression stage, and selectively, variably, or selectively and variably transferring heat from the primary coolant liquid to a fuel of the engine.
 2. The method of claim 1, further including transferring heat from the primary coolant liquid to a secondary coolant liquid.
 3. The method of claim 1, further including; determining a temperature of the inlet air, and varying the quantity of heat transferred from the primary coolant to the fuel of the engine as a function of the temperature of the inlet air.
 4. The method of claim 3, wherein the temperature of the inlet air includes a temperature of the inlet air after the first compression stage and before the second compression stage.
 5. The method of claim 3, wherein the temperature of the inlet air includes a temperature of the inlet air after the second compression stage.
 6. The method of claim 1, further including; determining the humidity of the inlet air, and varying the quantity of heat transferred from the primary coolant to the fuel of the engine as a function of the humidity of the inlet air.
 7. The method of claim 1, further including; determining a temperature of the primary coolant, and varying the quantity of heat transferred from the primary coolant to the fuel of the engine as a function of the temperature of the primary coolant.
 8. The method of claim 1, further including varying the flow of the primary coolant through a fuel cooled heat exchanger.
 9. The method of claim 1, further including varying the flow of the primary coolant through a fuel cooled heat exchanger bypass circuit.
 10. The method of claim 1, further including mixing the flow of the primary coolant exiting a fuel cooled heat exchanger with the flow of the primary coolant from a fuel cooled heat exchanger bypass circuit.
 11. An engine inlet air cooling system, comprising: a first compressor configured to pressurize inlet air, a second compressor configured to further pressurize the inlet air, and a cooling circuit including; a coolant heat exchanger configured to transfer heat from a primary coolant liquid, an inlet air heat exchanger configured to transfer heat from the inlet air to the primary coolant liquid after the inlet air exits the first compressor and before the inlet air enters the second compressor, and a fuel cooled heat exchanger configured to variably, selectively, or variably and selectively transfer heat from the primary coolant liquid to a fuel of the engine.
 12. The system of claim 11, further including; a primary coolant temperature sensor configured to generate a primary coolant temperature signal indicative of the temperature of the primary coolant, a controller configured to generate a fuel cooling command signal as a function of the primary coolant temperature signal, and a control valve assembly configured to vary the flow of the primary coolant liquid through the fuel cooled heat exchanger as a function of the fuel cooling command signal.
 13. The system of claim 11, further including; an inlet air temperature sensor configured to generate an inlet air temperature signal indicative of the temperature of the inlet air, a controller configured to generate a fuel cooling command signal as a function of the inlet air temperature signal, and a control valve assembly configured to vary the flow of the primary coolant liquid through the fuel cooled heat exchanger as a function of the fuel cooling command signal.
 14. The system of claim 11, further including; an inlet air humidity sensor configured to generate a an inlet air humidity signal indicative of the humidity of the inlet air, a controller configured to generate a fuel cooling command signal as a function of the an inlet air humidity signal, and a control valve assembly configured to vary the flow of the primary coolant liquid through the fuel cooled heat exchanger as a function of the fuel cooling command signal.
 15. The system of claim 11, further including a fan to direct a secondary coolant liquid through the coolant heat exchanger, the coolant heat exchanger configured to transfer heat from the primary coolant liquid to the secondary coolant liquid.
 16. An engine inlet air cooling system, comprising: an inlet air heat exchanger including a inlet air passage and a first primary coolant passage in thermal communication, a coolant heat exchanger including a second primary coolant passage, a fuel cooled heat exchanger including a fuel passage and a third primary coolant passage in thermal communication, an inlet air circuit including a first compressor configured to pressurize inlet air, the inlet air passage, and a second compressor configured to further pressurize the inlet air, wherein the inlet air passage fluidly connects the first compressor and the second compressor, a fuel circuit including the fuel passage, and a primary coolant circuit including; the first primary coolant passage, the second primary coolant passage fluidly connected to the first primary coolant passage, the third primary coolant passage fluidly connected to the first primary coolant passage, a fuel cooled heat exchanger bypass fluidly connected to the first primary coolant passage, and a control valve assembly selectively fluidly connecting the second primary coolant passage to the bypass, and selectively fluidly connecting the second primary coolant passage to the third primary coolant passage.
 17. The system of claim 16, further including a mixing valve fluidly connecting the first primary coolant passage to the bypass and the third primary coolant passage.
 18. The system of claim 16, wherein the fuel circuit includes a cryogenic fuel storage container fluidly connected to the fuel passage.
 19. The system of claim 16, wherein the fuel circuit includes a fueling device fluidly connected to fuel passage.
 20. The system of claim 16, wherein the inlet air circuit includes an inlet air cooler fluidly connecting the outlet of the second compressor with an intake manifold of the engine.
 21. An engine system, comprising: an engine including an intake manifold, and a fueling device a fuel source, a first compressor configured to pressurize inlet air, a second compressor configured to further pressurize the inlet air, the second compressor fluidly connected to the intake manifold, and a cooling circuit including; a coolant heat exchanger configured to transfer heat from a primary coolant liquid, a inlet air heat exchanger configured to transfer heat from the inlet air to the primary coolant liquid after the inlet air exits the first compressor and before the inlet air enters the second compressor, a fuel cooled heat exchanger configured to selectively transfer heat from the coolant liquid to a fuel of the engine, the fuel cooled heat exchanger fluidly connecting the fueling device and the fuel source. 